The mean age of 15 pupils in a class is 14.2 years. One new pupil
FURTHER MATHEMATICS
WAEC 2010
The mean age of 15 pupils in a class is 14.2 years. One new pupil joined the class and the mean changed to 14.1 years. Calculate the age of the new pupil.
- A. 12.4 years
- B. 12.6 years
- C. 13.2 years
- D. 14.1 years
Correct Answer: B. 12.6 years
Explanation
\(Mean = \frac{\text{sum of ages}}{\text{no of pupils}}\)
Let the sum of the ages of the 15 pupils be x and the sum of the 16 pupils be y.
\(\frac{x}{15} = 14.2 \implies x = 14.2 \times 15 = 213\)
\(\frac{y}{16} = 14.1 \implies y = 14.1 \times 16 = 225.6\)
\(\text{Age of new pupil} = 225.6 - 213 = 12.6\)
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